You have to authenticate to each account on your Bungie.net profile in order to set up Cross-Save.
You can unlink the incorrect Steam ID from your Bungie.net settings under Account Linking.
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Hey. Thanks for the reply. I can’t unlink the steam account because that account is gone.
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You'll need to work with Valve's Steam support to recover the account. If you cannot recover access to the account, you cannot unlink it, and Bungie will not forcefully do it for you.